I discovered this after I completed story mode, but if you go to niko's apartment in Algonquin and wait outside for about 20 minutes a hobo looking guy walks through the doors and just stands there until you kill him, and he's wearing nikos outfit in the beginning of the original GTA4. Is this some sort of game lag? or maybe its a weird easter egg. :/

Blue hell - Go to the hospital in schottler and bring grenades. Go right in the hospital. Go right again and you'll be in a hallway. A gurney will block you. Use the grenade. Throw it by the window. (Run off or you'll blow up) Smash the window if needed. Jump over the window and the citizens will be invisible and you can float in mid air. Go too far and you'll be on the streets.

Swing set glitch - Use a car or bike (Cabby and voodoo cars work) Hanging on to the swings are alright. Go to the park with two pairs of swing sets in Firefly Project in Hove Beach. Use the car/bike/yourself to back slam into the swings. Your car may flip. Known places it lands are on top of roofs or exploding into the ground. (another blue hell) If your car sets on fire in the park, get out and run far away. The car MAY glitch and fling at Niko. So be careful. Niko may die as well. (Especially if you're on a bike or you hang on)

This ones a type of glitch, if you push up on the left analog stick while above water, when the height meter is in the middle hit Y and when you land in the water you will be swimming under water. NOTE: You can't be shot.

Just a little trick for the parachute, if you tap both triggers repeatedly you start to ascend but if you go too high your parachute will disappear for some weird reason, its really useful for the parachute challenges though.

Hard to get ' one man army ' because cop drive By ?
well keep call henrique for APC after beating the story & stock it to all niko's safehouse
and luis's safehouse ( each safehouse Hold 2 APC )

or you can simply hunt 50 seagulls to spawn one in yusuf's construction
site near helitour maverick

tips :
if your APC start to smoking , you must quickly get to nearest safehouse ( which
contain APC ) . then , while entering . Tap X to quickly move to prevent cop
bust you inside / clear them out before you enter the Fresh tank

Hove Beach, Broker - Can be found across the street from the Broker Safehouse on Mohawk Ave, behind the wooden fence near the hot dog vendor and resting in an alcove against a building

SMG :

Schottler - Can be found on an air-conditioning ductwork in an alley between Boone St and Dillon St. This pickup isn't so tricky to get to: walk the alley opposite Jacob's home just to the dead end, jump to the left edge. you can't pull onto the roof near the roof windows so move along this edge left then pull up

Francis International Airport - Can be found on the top level of the parking garage to the southwest of the airport subway station

Micro-smg :

Beechwood City, Broker - Can be found in the alley behind the Homebrew Café on Dillon St

Francis International Airport, Dukes - Can be found under the Broker-Dukes Expressway, coming from Beechwood City

Combat shotgun :
Its simple , you just need steal police patrol / cruiser , once you enter one .
you'll get 5 shells each cars ( works for police stinge , police buffalo & enforcer )
this also useful in multiplayer to fills any kinds of shotguns (
including assault shotgun & explosive shotgun )

you need a baseball bat to kill clerk in back alley weapon store , kill him with
bath before he trigger the gun ( if a shots triggered by someone inside shop ,
his armed buddies will show up )

pistol :

its simple , you need find a Fat security guard & lure him to pull a gun (
be carefully )
Firefly Island - Can be found to the right of the "Liberty Go-Karts" wall mural to the right of Wappinger Ave.
Hove Beach - Can be found atop the Perestroika club, on a walkway on the roof.
Rotterdam Hill - Can be found across the street from Michelle's house in a gated lot, behind some dumpsters.
East Hook - Can be found on the first-floor ledge of a cylindrical silo-type structure off Mohanet Ave. The player can easily reach it with an SUV/MPV or other tall vehicle like a Cavalcade or Ambulance.
certain gang members carry this guns
getting a pistol from a cop is diffcult . you need lure someone who had their
firearm , then call 911 . cops will show off and they might be dead

Assault rifle :

After russian revolution , sometimes a russian will armed this . you need shotgun /
SMG / micro-smg to take him down and steal his rifle ( the reason why these
weapon recommended , their friend will notice you attacking them and they
will pull shotgun / pistol )

carbine rifle :

this one is hard . you need to find a cop in subway ( the fit one always carries carbine
, fat one never) , kill him with a knife / lure someone until they pulls their firearms
to make cop with carbine attack them . if cop die , steal his carbine

health :

some subways have first aid

saving games by sleeping restore players HP ( player cannot do this in multiplayers )

all hospital have first aid hinged somewhere in walls ( or even inside interior )

you could steal ambulance , its restore 25% HP

you can use your cash to call ambulance by 911 > 2 . wait and approach the
paramedic as he will heal you , if you don't want to . scare him ( < here )

so you don't want my suggestion in above ( ^ up there ) because its expensive ?
. well steal the ambulance once you call 911 > 2 to heal 25% HP

This is for bogt. First go on the highest building of liberty city but you need a parachute. When your done jump of the building and open your parachute fast as you can. Keep trying to go up. (You can also do this with a helicopter.)

Patrick "Packie" McReary : An Irish thug who is the heir to the declining Irish Mob of Liberty City. Those who know him refer to him as "Packie." Packie is the youngest of the McReary family and is related to corrupt police detective Francis McReary, Derrick McReary, Kate McReary and incarcerated ex-IRA member Gerry McReary. Packie lives with his mother and sister. Katie McReary, his sister, shows an "interest" in Niko, but he warns him away from her. Packie a close friend of Elizabeta. Packie is in the end of the 3rd trailer with 2 other Irish-looking gangsters who force Niko to join their gang. Known to take orders from Gerry who is in prison for the Liberty City Irish Mob.

The one man army trophy requires you to get a six star wanted level and survive for 5 mins without getting busted or killed. Sounds hard, but an easy way to get this is availiable from the start of the game. Use the cheat for weapons and armor a few times till you max out your ammo, save, quit and reload(this will reactivate the trophy) and stand outside romans apartment, fire a few shots to get a 1 star level, attract police and blast a few to get to about a 3. Now go into the apartment block and up to the apartment and use the refridgerator as cover and just blind fire with either a shotgun or M4 as the cops run in. Just keep this up till you get your six star and continue for 5 mins and the trophy will unlock. Do not use ammo or health cheats while doing this or you will disable the trophy!

Get a comet anialator our a nrg 900 go super fast (or high ) and push triangle (or Y) and go flying (warning you may die during the process) (when on the nrg 900 just hit a wall are something and you can fly and do better tricks:) )